Michel E. Hendrickx. Instituto de Ciencias del Mar y Limnología, Unidad Académica Mazatlán P.O. Box 811. Mazatlán, Sinaloa, 82000, Mexico

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1 Belg. J. Zool., 131 (Supplement 2): December 2001 Occurrence of a continental slope decapod crustacean community along the edge of the minimum oxygen zone in the south eastern Gulf of California, Mexico Michel E. Hendrickx Instituto de Ciencias del Mar y Limnología, Unidad Académica Mazatlán P.O. Box 811. Mazatlán, Sinaloa, 82000, Mexico ABSTRACT. Decapod crustaceans living in deep-water in the south eastern Gulf of California were collected during two research cruises in August 1991 and Benthic sledges were operated in the depth range of 550 to 2250 m. Vertical distribution of dissolved oxygen was obtained at selected stations and epibenthic oxygen content was measured at almost all sampling stations. A total of 31 species was collected, 21 strictly benthic and eight strictly pelagic. They belong to the Penaeoidea (five species), the Caridea (13 species), the Anomura (seven species), the Astacidea (one species), the Thalassinoidea (two species), the Eryonoidea (two species) and the Brachyura (one species). The oxygen minimum zone at bottom level represents a dispersal barrier for continental shelf species, including species known to have a wide bathymetric distribution. The deep-water decapod crustacean fauna (i.e., below 550 m) living along the offshore edge of this oxygen minimum zone is dominated by species of Munidopsis. The number of benthic species collected at the stations varied considerably, from zero to 15. The highest numbers of species were caught in the depth range of , where hypoxic ( ml O2/l) conditions prevailed. Stations with higher oxygen content had fewer benthic species. Factors other than oxygen content, affect the occurrence of species in the area. KEY WORDS: Decapod crustaceans, continental slope, southeastern Gulf of California, hypoxia. INTRODUCTION While the northern part of the Gulf of California is relatively shallow, with the exception of the Delfin basin, the central and southern parts increase in average depth towards the mouth of the Gulf. Several deep basins are found offshore with depths reaching 3000 m or more. The southern Gulf of California opens to the Pacific, with depths greater than 3000 m at the entrance (PARKER, 1964; ALVAREZ-BORREGO & SCHWARTZLOSE, 1979). In the southern Gulf, water temperature does not show any special structure. It decreases monotonically with depth and reaches values of less than 10 C below m. There is an orderly progression to the deepest portions of the Gulf of from 10 C to <4 C at 2000 m. The southernmost basin, from about 26º N to the mouth of the Gulf, has epibenthic water temperatures of 2 C or less, characteris- Corresponding author: M. Hendrickx, michel@mar.icmyl.unam.mx tic of the bottom water of the equatorial Pacific (PARKER, 1964). Epibenthic dissolved oxygen concentration has been recognized as a major limiting factor for benthic and demersal species. Although it is generally admitted that respiration in most marine invertebrates is not significantly affected until extremely low oxygen concentrations are reached, i.e. below 2.0 ml/l or even less (ROSENBERG et al. 1991; DIAZ & ROSENBERG, 1995), decreasing oxygen content near the bottom or in the water column can create an anoxic zone where no macrofauna occur (DIAZ & ROSENBERG, 1995). Species diversity at depths from 100 m to 2140 m off the coast of Southwest Africa, and at depths of m in the Santa Catalina Basin, off California, has been shown to decline with reduced oxygen content of the bottom water or to be lower than adjacent areas where oxygen content is higher (JUMARS, 1976; GRASSLE, 1989). Oxygen minimum zones have long been recognized in different parts of the world, either in fjords, coastal water

2 96 Michel E. Hendrickx or in open ocean. The widest area where severe hypoxia has been observed is in the east Pacific (WYRTKI, 1966; KAMYKOWSKI & ZENTARA, 1990). Severe hypoxia can drastically reduce diversity and size of natural communities (see NILSSON & ROSENBERG, 1994). Since deep water crustaceans were collected by the Albatross in 1891 off the coast of Mexico to Peru, almost no studies have been performed in the southern Gulf of California. The most complete study of the deep water fauna of the east Pacific slope is by PARKER (1964), based on series of 11 samples obtained on the middle continental slope ( m), and of 19 samples obtained between 1800 and 4122 m in the abyssal southern basins and outer slope of the Gulf of California. Parker s definition of assemblages, however, was based mostly on molluscs and the occurrence of decapod crustaceans must be inferred from a long data matrix (Parker, 1964: Table 7) and related to a map of sampling stations. He found 14 species of decapod crustaceans below 500 m of which only two were recorded in the Southeastern Gulf of California. WICKSTEN (1989) provided a synthesis of all species of eastern Pacific decapod crustaceans with the majority of records at 50 m or deeper (defined as offshore species ). A total of 183 species is included, of which 117 have records in the depth category of m, 96 at m and 46 at depths >1500 m (WICKSTEN, 1989). An analysis of habitats and biodiversity of decapod crustaceans in the Southeastern Gulf of California (HENDRICKX, 1996a) reported that 19 deepwater species were collected between 200 and 1200 m, some of which represent new records for the area (HENDRICKX, 1996b). An oxygen minimum zone has long been recognized in the Gulf of California. According to PARKER (1964), this zone of low oxygen concentration (ca. 0.5 ml/l) at or near the bottom forms a fringe parallel to the coast that extends, on both sides of the Gulf, from the east and west entrances to ca. 29 N. Up to 90 km wide, it mostly covers the outer continental shelf and the upper slope, roughly from 100m to 500 or 1000 m, depending on location. Recent studies, however, indicate that almost anoxic conditions are occasionally found on the shelf at 60 m (HENDRICKX et al., 1984; GARDUÑO-ARGUETA & CALDERÓN PÉREZ, 1995). The purpose of this study is to define the deepwater decapod crustacean community that occurs on the offshore side on the oxygen minimum, roughly in the depth range of 550 to 2200 m, in the SE Gulf of California. METHODS Crustaceans samples were dredged at depths of 550 to 2250 m in the SE Gulf of California. Material was obtained during two cruises aboard the R/V El Puma of the Universidad Nacional Autónoma de Mexico. Samples were obtained with benthic sledges at 11 stations in August 1991 (TALUD III cruise) and at eight stations in August 2000 (TALUD IV), off the coast of Sinaloa, Mexico (Table 1). The sledges were operated at depths from 550 to 1380 m (TALUD III) and from 785 m to 2250 m (TALUD IV). Two different benthic sledges were used: a 2.5 m wide by 1.0 m high modified Agassiz sledge equipped with a collecting net of ca. 5.5 cm (2 1/4 ) stretch mesh lined with ca. 2.0 cm (3/4 ) mesh net (TALUD III) and a 2.35 m wide by 0.95 m high standard benthic sledge equipped with a collecting net of ca. 5.5 cm (2 1/4 ) stretch mesh lined with ca. 2.0 cm (3/4 ) mesh net in the mouth area (TALUD IV). At selected sampling stations of the TALUD III cruise and at all sampling stations of TALUD IV cruise, a previously calibrated CTD probe equipped with an oxygen sensor was used to obtain temperature, salinity and dissolved oxygen profiles from surface to near bottom level. During the TALUD IV cruise, an opening-closing bottle was used to obtain near bottom water samples used to measure the dissolved oxygen by the Winkler method (duplicate samples). During the TALUD III cruise, oxygen measurements were obtained from the pre-calibrated probe (a SEB Seacat Profiler) and are considered reliable for biological interpretation. The CTD probes and opening-closing bottle were not operated less than 15 m off the bottom. TABLE 1 Sampling stations where decapod crustaceans were caught during the TALUD III and IV cruises. Position Station Date Lat. N Long. W 10/III 18/Aug/ A/III 18/Aug/ A/III 19/Aug/ B/III 19/Aug/ /III 20/Aug/ A/III 24/Aug/ ,06 24/III 21/Aug/ A/III 24/Aug/ /IV 23/Aug/ /IV 24/Aug/ /IV 24/Aug/ /IV 25/Aug/ /IV 25/Aug/ /IV 25/Aug/ /IV 26/Aug/ /IV 26/Aug/ /IV 26/Aug/ /IV 27/Aug/ /IV 27/Aug/ /IV 27/Aug/ Crustaceans were sorted onboard, preserved in diluted formaldehyde or in 70% ethanol. A list of all species is tabulated with accompanying data. Body lengths were measured with vernier calipers, usually to the nearest

3 Continental slope decapod crustaceans southeastern Gulf of California mm. Carapace length was measured in shrimps while total length was used with lobsters and galatheids. The identified specimens form part of the collections of the Mazatlán Marine Station, UNAM. Only species collected during the TALUD IV cruise and of special interest were treated individually in the systematic section. Biogeographic or ecological data related to species collected during the TALUD III cruise have been reported elsewhere (see HENDRICKX, 1996b). Data on other species captured during these cruises are summarized and included in a general table with their respective collecting data. Abbreviations used: St., sampling station; CL, carapace length; TL, total length; BS, benthic sledge. Systematic section RESULTS PENAEOIDEA Family Solenoceridae Hymenopenaeus doris (Faxon, 1893) Haliporus doris FAXON, 1893: 214. Haliporus doris. FAXON, 1895: 191, pl. 49, Figs. 1-1c. Hymenopenaeus doris. BURKENROAD, 1936: 104; 1938: 60. PÉREZ-FARFANTE, 1977: 283, Figs. 9, 17a, 18a, MÉNDEZ, 1981: 55, Figs. 155, 156, 156a-c. HANAMURA, 1983: 55, Fig. 2. WICKSTEN, 1989: 311. WICKSTEN & HENDRICKX, 1992: 4. HENDRICKX, 1993: 305; 1995d: 529, Fig. 1b, 530, Fig. 3b, 531, Fig. 8a, 532, Fig. 9a, 534; 1996c: 119, Fig. 60. HENDRICKX & ESTRADA-NAVARRETE, 1996: 40, Fig. 24. Aliporus doris. DEL SOLAR, 1972: 4. Material examined. St. 19-IV, 25/VIII/2000, 1 male (CL 13.5 mm) and 1 female (CL 12.0 mm), m, BS. Previously known distribution. From Punta Chivato, Mexico to Guanape, Peru (HENDRICKX, 1996c). Remarks. The only records in benthic samples for the Gulf of California are off Punta Arena and Punta Chivato, along the Baja California Peninsula (HENDRICKX, 1996c). The species has also been captured in the water column (see HENDRICKX & ESTRADA-NAVARRETE, 1996) and its presence in bottom trawls might be due to incidental catch during recovery of the gear. Family Benthesicymidae Benthesicymus tanneri Faxon, 1893 Benthesicymus tanneri FAXON, 1893: 215. Benthesicymus tanneri. FAXON, 1985: 205, Fig. H. RATHBUN, 1904: 147. SCHMITT, 1921: 23, Fig. 10. MÉNDEZ, 1981: 31. RODRÍGUEZ DE LA CRUZ, 1987: 20. WICKSTEN & HENDRICKX, 1992: 2. HENDRICKX, 1993: 305; 1995d: 436, Fig. 4, 437; 1996c: 12, Fig. 5. Material examined. St. 13-IV, 24/VIII/2000, 1 male (CL 31.8 mm), m, BS; St. 19-IV, 25/VIII/2000, 3 females (CL mm), m, BS; St. 26-IV, 26/VIII/2000, 1 male (CL 30.2 mm) and 2 juveniles (not measured), m, BS; St. 33-IV, 27/VIII/2000, 2 males (CL 33.2 and 34.8 mm), 1040 m, BS. Previously known distribution. From San Diego, California, USA to Ilo, Peru. Southeastern Gulf of California; Galapagos Islands (HENDRICKX, 1996c). Remarks. The distribution of this species is synthesized by HENDRICKX (1996c). Benthesicymus tanneri is a common species in deep water of the SE Gulf of California. Material captured during this study includes the largest specimens known to date (up to 135 mm TL). Adult specimens are rather heavy (ca g of individual fresh weight for specimens of mm TL) and they most probably live close to the bottom. Often captured with Heterocarpus affinis, a potential deep-water resource in the eastern tropical Pacific (HENDRICKX 1995d), B. tanneri could represent an interesting by-catch species in pandalids fishery. CARIDEA Family Pandalidae Pandalus amplus (Bate, 1886) Pandalopsis amplus BATE, 1888: 671, pl. 175, Fig. 3. Pandalopsis ampla. FAXON, 1895: 155. RATHBUN, 1904: 51. SCHMITT, 1921: 46. WICKSTEN, 1989: 313. WICKSTEN & HENDRICKX, 1992: 9. Material examined. St. 19-IV, 25/VIII/2000, 2 females, the smallest ovigerous (CL 31.6 and 32.6 mm), m, BS. Previously known distribution. From Sea Lion Rock, Washington, USA to Acapulco, Gro., Mexico. ATL from off Montevideo, Uruguay to Argentina (WICKSTEN & HENDRICKX, 1992). Remarks. Pandalus amplus is a common species off the coast of California, where it has been reported at least in 28 localities (HENDRICKX & WICKSTEN, 1989) and from a depth range of m. There are only five records along the Pacific coast of Mexico, including two in the Gulf of California. The present record represents a range extension of this species along the east coast of the Gulf of California to N W. The size of the largest female (165 mm TL) is close to the maximum known size (170 mm TL) for the east Pacific. Fresh weight of specimens examined are 22 and 24 g. Family Crangonidae Sclerocrangon atrox Faxon, 1893 Sclerocrangon atrox Faxon, 1893: 199. Sclerocrangon atrox. FAXON, 1895: pl. 35, Figs. 1, 1a-f. MÉNDEZ, 1981: 121. WICKSTEN & HENDRICKX, 1992: 6. Material examined. St. 13-IV, 24/VIII/2000, 1 male (CL 27.8 mm), m, BS; St. 19-IV, 25/VIII/2000, 1 male (CL 25.2 mm), m, BS. Previously known distribution. From near Tres Marias Islands, Nayarit, Mexico to off Mollendo, Peru (WICKSTEN & HENDRICKX, 1992).

4 98 Michel E. Hendrickx Remarks. A large (up to 162 mm TL; ca. 38 mm CL) and rather rare species of Crangonidae. The present material increases the range northwards by two degrees of latitude, from off Tres Marias Islands to 24º15.3 N - 108º24.1 W. Family Oplophoridae Acanthephyra brevirostris Smith, 1885 Acanthephyra brevirostris SMITH, 1885: 504. Acanthephyra brevirostris. SMITH, 1886(1887): 670, pl. 14, Fig. 2, pl. 15, Figs. 2, 8, pl. 16, Figs. 1, 6. FAXON, 1895: 167. KENSLEY, 1972: 38, Fig. 17m. CROSNIER & FOREST, 1973: 41, Figs. 8c-d. HANAMURA, 1983: 75. CHACE, 1986: 8 (Key), Figs. 2e, 4e, 5e, 6d, 8d. HENDRICKX & ESTRADA-NAVARRETE, 1989: 113; 1996: 109, Fig. 67. Material examined. St. 26-IV, 26/VIII/2000, 1 juvenile (CL 6.5 mm), m, BS. Previously known distribution. From off Baja California and off Ecuador, including the SE Gulf of California; SW Indian Ocean; East and West Atlantic Ocean (HENDRICKX & ESTRADA- NAVARRETE, 1996). Remarks. Only two records of this species are available for the east Pacific (off Ecuador, 0.58 S E; Dowd Tablemount, off Baja California, Mexico) (HENDRICKX & ESTRADA NAVARRETE, 1996). The juvenile examined, although slightly damaged, shows features distinctive of this species. This deep-water pelagic species has been collected between 1280 and 5394 m, mostly in mid-water trawls. Examined material was most probably collected in the water column during recovery of the dredge. Hymenodora gracilis Smith, 1887 Hymenodora gracilis SMITH, 1886 (1887): 680, pl. 12, Fig. 6. Hymenodora gracilis. SIVERTSEN & HOLTHUIS, 1956: 16, Figs. 12, 13. CROSNIER & FOREST, 1973: 83, Fig. 25a. WASMER, 1986: 49, Figs. 10b-c. CHACE, 1986: 43 (clave), Figs. 21p-t. IWASAKI & NEMOTO, 1987a: 20. KRYGIER & WASMER, 1988: 87. HANAMURA, 1989: 54, Fig. 2. HENDRICKX & ESTRADA-NAVARRETE, 1989: 115; 1996: 119, Fig. 73. ALLEN & BUTLER, 1994: 426, Fig. 5. Material examined. St. 35-IV, 27/VIII/2000, 1 male (CL 12.0 mm), m, BS. Previously known distribution. From Oregon, USA to West coast of Baja California; coast of Chile and in subantarctic waters of the South Pacific Ocean (HENDRICKX & ESTRADA- NAVARRETE, 1996). Remarks. This is the first record outside the temperate waters of the NE and SE Pacific. A mesopelagic and bathypelagic species, H. gracilis is reported from ca. 300 to 5300 m (HENDRICKX & ESTRADA NAVARRETE, 1996). Some of these depth records, however, might be erroneous caused by the use of non-closing, bottom sampling devices. The material reported here was accidentally captured in the bottom sledge and there is no way to assess correctly the depth at which it was collected. Hymenodora glacialis, a closely related species, has been previously recorded in the central Gulf of California (HENDRICKX & ESTRADA NAVARRETE, 1996). Family Pasiphaeidae Pasiphaea emarginata Rathbun, 1902 Pasiphaea emarginata RATHBUN, 1902: 905. Pasiphaea emarginata. RATHBUN, 1904: 22, Fig. 4. SCHMITT, 1921: 30, Fig. 15. CHACE, 1937: 110. WORD & CHARWAT, 1976: (Illustration). HENDRICKX & ESTRADA-NAVARRETE, 1989: 111; 1996: 89, Fig. 55. Material examined. St. 25-IV, 26/VIII/2000, 2 males (CL 35.1 and 36.0 mm) and 10 females (CL mm), m, BS. Previously known distribution. From West coast of Baja California (up to 26 N) and in the Gulf of California (up to N); south to the Gulf of Panama and Lobos de Tierra Islands, Peru; Galapagos Islands (HENDRICKX NAVARRETE, 1996). & ESTRADA- Remarks. In addition to the type material taken near Concepcion Bay entrance, the only other two records of this species in the Gulf of California are over 60 years old (CHACE, 1937); all these records are from the central Gulf. Pasiphaea magna Faxon, 1893 Pasiphaeia magna FAXON, 1893: 209. Pasiphaea magna. FAXON, 1895: 176, pl. 45, Fig. 2. WORD & CHARWAT, 1976: 208. MÉNDEZ, 1981: 64, Figs KRYGIER & WASMER, 1988: 77. HENDRICKX & ESTRADA-NAVARRETE, 1989: 111; 1996: 91, Figs. 56, 57. Material examined. St. 19-IV, 25/VIII/2000, 1 female (CL 31.1 mm), m, BS. Previously known distribution. From Oregon, USA, and the SE Gulf of California to the Gulf of Panama and Peru (HENDRICKX & ESTRADA-NAVARRETE, 1996). Remarks. This is the second record of P. magna in Mexican waters (see HENDRICKX & ESTRADA-NAVARRETE, 1996). Maximum recorded size is 185 mm (TL). The examined specimen is 106 mm TL. Family Hippolytidae Lebbeus scrippsi Wicksten & Méndez, 1982 Lebbeus scrippsi WICKSTEN & MÉNDEZ, 1982: 106. Lebbeus scrippsi. WICKSTEN, 1989: 312. HENDRICKX, 1996b: 946. Material examined. St. 19-IV, 25/VIII/2000, 4 males (CL mm) and 3 ovigerous females (CL mm), m, BS; St. 26-IV, 26/VIII/2000, 2 males (CL 6.7 and 10.3 mm), m, BS. Previously known distribution. From Peru to Chile; one record in southeastern Gulf of California (WICKSTEN, 1989; HENDRICKX, 1996b). Remarks. This rare species is again reported in the area; two females (CL 9.0 and 9.4 mm), including one ovigerous, were reported in Among the 9 specimens reported here are 3 ovigerous females carrying eggs each (Table 2). The largest female from station 26 (CL 10.9 mm) is 42.0 mm TL, slightly longer than the largest paratype (TL 41.2 mm).

5 Continental slope decapod crustaceans southeastern Gulf of California 99 TABLE 2 Sizes by sex, eggs number and eggs size in Lebbeus scrippsi from the Gulf of California continental slope (M, male; F, female). Sex CL/TL(mm) Eggs Number Size range (mm) M 6.7/ M 7.0/ M 8.2/ M 8.2/ F 9.5/ F 10.0/ F 10.9/ M 10.3/ M 6.75/ Family Glyphocrangonidae Glyphocrangon sicaria Faxon, 1893 Glyphocrangon sicarius Faxon, 1893: 202. Glyphocrangon sicaria. FAXON, 1895: pl. 39, Figs. 1, 1a-e. WICKSTEN, 1989: 314. WICKSTEN & HENDRICKX, 1992: 6. Material examined. St. 14-IV, 24/VIII/2000, 1 specimen not sexed (CL 6.5 mm), m, BS; St. 26-IV, 26/VIII/00, 1 specimen not sexed (CL 9.0 mm), m, BS. Previously known distribution. From South of Punta Guiones, Costa Rica to Gulf of Panama (WICKSTEN & HENDRICKX, 1992). Remarks. One of the 5 species of the genus reported for the eastern tropical Pacific, G. sicaria has so far been reported exclusively below ca m ( m; WICKSTEN, 1989). Remarks. The material is assigned to N. ensiger with some doubts. It includes specimens with no ventral teeth on the rostrum and others with 1-3 clearly distinguishable small teeth in the distal portion. According to CROSNIER and FOREST (1973), presence of ventral teeth on some Albatross specimens, reported by FAXON (1895) as belonging to an atypical form of N. ensifer from the east Pacific, should be linked with the presence, in this area, of another species. A revision of W. Faxon material by R. Burukovsky (pers. comm. October 2000) prompted this author to describe a new species (forthcoming manuscript) close to N. agassizi Faxon, 1893, the second species of this genus previously reported in the east Pacific. Although our material features a rostrum clearly distinct from N. agassizi, a careful revision of the specimens collected during both TALUD cruises (see HENDRICKX, 1996b) should be undertaken. Although the dorsal process on the posterior margin of the third abdominal segment is similar in large, adult specimens, the rostrum features either long dorsal spines and a few ventral spines, or short dorsal spines on a longer rostrum and no ventral spines (Fig. 1). As noted by R. Burukovsky, species of Nematocarcinus are difficult to identify, mostly because they are generally damaged during sampling (loss of pereiopods). Family Nematocarcinidae Nematocarcinus cf. ensifer (Smith, 1882) Eumiersia ensifera SMITH, 1882: 77, pl. 13, Figs Nematocarcinus ensiferus. SMITH, 1884: 368, pl. 7, Fig. 1. Nematocarcinus ensifer. CROSNIER & FOREST, 1973: 116, Figs, 32a-c, 33a-c. WICKSTEN & HENDRICKX, 1992: 6. Material examined. All specimens unsexed and unmeasured. St. 13-IV, 24/VIII/2000, 6 specimens, m, BS; St. 26-IV, 26/VIII/2000, 5 specimens, m, BS; St. 33- IV, 27/VIII/2000, 2 specimens, 1040 m, BS; St. 34-IV, 27/VIII/2000, 1 specimen, m, BS. Previously known distribution. Nematocarcinus ensifer is known from off Acapulco, Mexico, to the Galapagos Islands; distributed worldwide (Atlantic, Pacific, Indian Ocean and Mediterranean Sea (WICKSTEN & HENDRICKX, 1992). Fig. 1. A, C) Anterior part of carapace and rostrum of Nematocarcinus cf. ensifer. B, D) Dorsal view of 3rd abdominal tergite (A, B, St. 34. CL 16.6 mm; C, D, St. 26, CL 22.2 mm).

6 100 Michel E. Hendrickx ERYONOIDEA Family Polychelidae Stereomastis pacificus (Faxon, 1893) Polycheles sculptus pacificus Faxon, 1893: 196. Polycheles sculptus pacificus. FAXON, 1895: 122, pl. C, Fig. 1, 1a. Eryoniscus agassizi. SCHMITT, 1921: 105, pl. 15, Figs Stereomastis sculpta pacifica. WICKSTEN, 1981: 914, Fig. 1; 1989: 311. HENDRICKX, 1995a: 156. Material examined. St. 19-IV, 25/VIII/00, 1 male (TL mm), 2 females (CL and mm) and 1 ovigerous female (CL mm), m, BS. Previously known distribution. From San Clemente Island, California, USA, to Valparaiso, Chile. Off Tres Marias Islands (HENDRICKX, 1995a). Remarks. There is a total of 41 records of S. pacificus from the east Pacific (off the coasts of southern California, USA, Mexico, Panama, Costa Rica, Colombia, Peru and Chile) (see WICKSTEN, 1981), thus indicating that it has been frequently caught within its range. Original records by FAXON (1893) include one from the SE Gulf of California, off Tres Marias Islands; this is believed to be the only published record for this species within the Gulf of California. WICKSTEN (1981) mentioned a series of 32 adults from 20 stations in Costa Rica, Mexico and southern California, but without further details. ANOMURA Family Galatheidae Munidopsis ciliata Wood-Mason, 1891 Munidopsis ciliata WOOD-MASON, 1891: 200. Munidopsis ciliata. FAXON, 1895: 84, pl. 18, Fig. 3. BENEDICT, 1902: 318. AMBLER, 1980: 19, Fig. 3. WICKSTEN, 1989: 315. HENDRICKX & HARVEY, 1999: 376. Munidopsis brevimana. HENDERSON, 1885: 414; 1888: 154, pl. 17, Figs. 1, 2. Munidopsis (Orophorhynchus) ciliata. ALCOCK, 1901: 267. Material examined. St. 19-IV, 25/VIII/00, 2 males (TL 45.7 and 52.3 mm) and 1 ovigerous female (TL 58.8 mm), m, BS. Previously known distribution. From Oregon, USA to off Panama, including the southern Gulf of California (WICKSTEN, 1989). Remarks. Within its geographic range, M. ciliata had been reported from a depth range of m (WICKSTEN, 1989). The present record is from much shallower water. The ovigerous female carried 56 eggs. Munidopsis depressa Faxon, 1893 Munidopsis depressa FAXON, 1893: 189. Munidopsis depressa. FAXON, 1895: 96, pl. 22, figs 2, 2a, 2b. BENEDICT, 1902: 319. WICKSTEN, 1989: 315. HENDRICKX, 1996b: 946. HENDRICKX & HARVEY, 1999: 376. Material examined. St. 25-IV, 26/VIII/2000, 205 males (TL mm), 64 females (TL mm) and 4 ovigerous females (TL mm), m, BS; St. 26-IV, 26/VIII/2000, 33 males (TL mm), 13 females (TL mm) and 3 ovigerous females (TL mm), m, BS. St. 33-IV, 27/VIII/2000, 1 male (TL 36.0 mm) and 1 ovigerous female (TL 38.0 mm), 1040 m, BS. Previously known distribution. From off Santa Catalina Island, California, USA, to the Gulf of California, Mexico, from off Ahome Point, Sinaloa, to off Tres Marias Islands (HENDRICKX, 1996b). Remarks. Five samples were obtained during the previous cruise (TALUD III) at depths between 820 and 1208 m in the same area (HENDRICKX, 1996b). Considering these records and the new material obtained during this study, M. depressa appears to be one of the most common and abundant species of decapod crustacean on the continental slope in the SE Gulf of California. Fig. 2. Lateral view of Munidopsis depressa. A) Specimen with unusually strong and long spines on carapace and a dorsal tooth on 5th abdominal segment (St. 33). B) Type material (after Faxon, 1893).

7 Continental slope decapod crustaceans southeastern Gulf of California 101 Specimens from stations 26 and 33 represent a spinose form of M. depressa. Spines on the carapace are much stronger and more numerous; also, the dorsal teeth on the abdominal segments are much stronger and there is one dorsal tooth on the fourth segment (Fig. 2), while material from the other stations lack this tooth, as does the type material illustrated by FAXON (1893). Close examination of these spinose specimens, including shape of the third maxilliped, the basal article of the antenna and antennula, the sternum and the chelipeds, indicates that this spinose form corresponds to an extreme variation of M. depressa. Of the total (324 specimens), 239 specimens were males (74%). Only 8 ovigerous females were collected. Number of eggs varied from 21 to 29 in the smallest females (i.e., TL 27.0 to 33.0 mm) to 68 in the larger specimen collected at station 33; three hatching females had only 7 eggs retained on the pleopods. Munidopsis palmatus Khodkina, 1973 Munidopsis palmatus KHODKINA, 1973: , Figs 5-6. Material examined. St. 19-IV, 25/VIII/00, 1 ovigerous female (TL 22.0 mm), m, BS; St. 26-IV, 26/VIII/2000, 1 ovigerous female (TL 24.0 mm), m, BS. Previously known distribution. Known only from the type locality, off the coast of Chile, north of Valparaiso (32º11 6 S 71º46 3 W). Characteristics. Rostrum triangular in dorsal view, about 1/3 carapace length. Carapace as long as wide; gastric and cardiac regions raised, strong antero-branchial protuberance, granulated, tipped with spine or blunt tubercle. Antennal spine blunt or obsolete; protuberance at antero-lateral angle tipped with strong tooth, curved inside; lateral margin posterior to cervical groove entire, granulated. Dorsal carapace roughly granulated; cervical groove poorly marked, pair of large, strong gastric tubercles and conical median tubercle beyond this pair; posterior margin raised,. Surface of sternite 4-6 smooth; sternites 5 to 7 with transverse ridges minutely granulate, not raised. Abdominal segments without spines or tubercles, punctate; transverse ridge on segments 2-4 strong. Eyes small, without pigmentation and without spines, diameter less than 1/2 length of rostrum. Antennular basal segment broad, bearing large ventro-internal spine with accessory spinules, sharp external spine and two distal spines, dorsal one directed upwards; outer margin granulated. Outer distal spine of basal antennal peduncle strong, sharp, not reaching distal margin of 3rd segment of antennular peduncle. Merus of third maxiliped with two strong spines on flexor margin (no distal spine); extensor margin armed with one distal spine. Fig. 3. Munidopsis palmatus. A, Dorsal view. B) Left cheliped, dorsal view, and ventral view of merus. C) Left third maxilliped, lateral view. D) Right basal segment of antennula, dorsal view. E, Left antenna basal segments, dorsal view (scale = 2 mm).

8 102 Michel E. Hendrickx Cheliped about three times as long as carapace, granulated; merus with 5-6 sharp spines on inner margin, one distal. Carpus without spine; chela without spines, longer than merus, flat; palm slightly longer than fingers, wider distally. Lower and upper margin of manus spineless; fingers flattened, ventral margin of fixed finger and dorsal margin of dactylus spineless. Carpus subcylindrical, about 2/3 length of palm; dactylus shorther than palm. Pereiopods slender, without spines. Propodus about 3/4 merus length; dactylus falciform, more than half propodus length. Remarks. This species, together with three other species described from off the coast of Chile by KHODKINA (1973: M. verrucosus, M. cochlearis and M. follirostris) was overlooked by RETAMAL (1981) and WICKSTEN (1989) in their respective review of the decapod crustaceans of Chile and analysis of the deep-water decapod crustaceans fauna of the east Pacific. The rediscovery of M. palmatus, previously known only from the male holotype (8.9 mm CL), in the SE Gulf of California indicates that this species is probably distributed throughout the east Pacific. The original description was in Russian, so the characteristics distinguishing this species from other Munidopsis present in the area are presented above. Both specimens were ovigerous females. The specimen from station 19 carried 7 eggs but had obviously started hatching prior to capture; the female from station 26 carried 12 eggs. Munidopsis quadrata Faxon, 1893 Munidopsis quadrata FAXON, 1893: 188. Munidopsis quadrata. FAXON, 1895; pl. 23, Figs. 1, 1a-c. BENEDICT, 1902: 325. HART, 1982: 38. WICKSTEN, 1989: 315. HENDRICKX & HARVEY, 1999: 376. Material examined. St. 26-IV, 26/VIII/2000, 1 male (TL 31.0 mm), m, BS. Previously known distribution. From Queen Charlotte Islands, Canada to Tres Marias Islands, Gulf of California, Mexico (WICKSTEN, 1989; HENDRICKX & HARVEY, 1999). Remarks. The rediscovery of M. quadrata in the southern Gulf of California confirms the presence of this temperate species in deep water of tropical Mexico. It is the first record of this species here since it was described by FAXON (1893) from 4 specimens captured at m off Tres Marias Islands, Mexico. The male specimen reported here is slightly larger than the type material. Other collected species In addition to the 16 species treated above in the systematic section, the material from the TALUD IV cruise included nine species (see Table 3) that are briefly treated here. Two species of the strictly pelagic Sergestidae were captured. According to HENDRICKX & ESTRADA-NAVARRETE (1996), Sergestes halia Faxon, 1893, is a common species in the southern Gulf of California and extend throughout the eastern tropical Pacific. Sergia phorca (Faxon, 1893) shows a similar distribution pattern along the Pacific coast of America, but extends much further southwards, to southern Peru. Gennadas sordidus Kemp, 1910, is the only species of Gennadas known to the Gulf of California where it occurs abundantly except in the upper Gulf (HENDRICKX & ESTRADA-NAVARRETE, 1996). Adaptation of this species to low oxygen content in the water column consists of a strong increase of branchial surface (HANAMURA, 1983). The rest of the species (Heterocarpus affinis Faxon, 1893; Acanthephyra brevicarinata Hanamura, 1984; Glyphocrangon spinulosa Faxon, 1893; Munidopsis diomedeae (Faxon, 1893); M. hystrix Faxon, 1893; Nephropsis occidentalis Faxon, 1893) were also captured during the TALUD III cruise in the same area (Table 4). TABLE 3 Species of decapod crustaceans collected during the TALUD IV cruise in the SE Gulf of California. Oxygen measured at bottom level. M = male; F = female; FF = ovigerous female; juv. = juvenile. Species Station Depth Oxygen Material examined (size) content Benthesicymidae Gennadas sordidus ,46 1 F (CL 9.8 mm) Gennadas sordidus ,03 2 M (CL 9.0, 9.5 mm); 1 F (CL 9.8 mm) Gennadas sordidus ,73 1 juv. (CL 8.5 mm) Benthesicymus tanneri ,46 see text Benthesicymus tanneri ,73 see text Benthesicymus tanneri ,76 see text Benthesicymus tanneri ,51 see text Solenoceridae Hymenopenaeus doris ,73 see text Sergestidae Sergestes halia ,84 Sergia phorca ,76 1 F (CL 16.0 mm) Pasiphaeidae Pasiphaea emarginata ,29 see text Pasiphaea magna ,73 see text

9 Continental slope decapod crustaceans southeastern Gulf of California 103 Species Station Depth Oxygen Material examined (size) content Oplophoridae Acanthephyra brevicarinata ,73 1 M (CL 20.7 mm); 1 F (CL 28.1 mm) Acanthephyra brevicarinata ,26 1 M (CL 27.8 mm) Acanthephyra brevicarinata ,76 2 FF (CL 22.0, 22.2 mm) Acanthephyra brevicarinata ,32 1 juv. (TL 45.0 mm) Acanthephyra brevicarinata ,51 1 FF (CL 21.5 mm) Acanthephyra brevicarinata ,79 1 M (CL 11.2 mm) Acanthephyra brevicarinata ,68 1 F (CL 11.7 mm) Acanthephyra brevirostris ,76 see text Hymenodora gracilis ,68 see text Nematocarcinidae Nematocarcinus cf. ensifer ,46 see text Nematocarcinus cf. ensifer ,76 see text Nematocarcinus aff. ensifer ,76 see text Nematocarcinus cf. ensifer ,51 see text Hippolytidae Lebbeus scrippsi ,73 see text Lebbeus scrippsi ,76 see text Pandalidae Heterocarpus affinis ,29 1 F (CL mm) Heterocarpus affinis ,51 14 specimens (CL mm) Pandalus amplus ,73 see text Crangonidae Sclerocrangon atrox ,46 see text Sclerocrangon atrox ,73 see text Glyphocrangonidae Glyphocrangon sicaria ,44 see text Glyphocrangon sicaria ,76 see text Glyphocrangon spinulosa ,73 2 F (CL 22.4, 22.9 mm) Glyphocrangon spinulosa ,76 3 F (CL 17.1, 17.9 mm); 1 FF (CL 26.6 mm) Nephropidae Nephropsis occidentalis ,73 2 M (CL 32.3, 33.2 mm); 1 F (CL 35.5 mm) Nephropsis occidentalis ,76 1 F (CL 33.3 mm) Polychelidae Stereomastis pacificus ,73 see text Paguridae Parapagurus foraminosus ,44 1 FF (CL 7.4 mm) Galatheidae Munidopsis ciliata ,73 see text Munidopsis depressa ,29 see text Munidopsis depressa ,76 see text Munidopsis depressa ,51 see text Munidopsis diomedeae ,73 1 M (TL 65.0 mm) Munidopsis diomedeae ,26 1 FF (TL 73.0 mm) Munidopsis diomedeae ,76 1 juv. (TL 19.9 mm) Munidopsis hystrix ,29 4 M (TL mm) Munidopsis hystrix ,76 1 M (TL 59.0 mm) Munidopsis palmatus ,73 see text Munidopsis palmatus ,76 see text Munidopsis quadrata ,76 see text

10 104 Michel E. Hendrickx TABLE 4 Species of decapod crustaceans collected during the TALUD III cruise in the SE Gulf of California. Species marked with an * have been reported in details elsewhere (see Hendrickx, 1996b). Species Station Depth Oxygen content (ml/l) Benthesicymidae Benthesicymus tanneri 14A ,40 Benthesicymus tanneri 14B ,60 Benthesicymus tanneri 24A Oplophoridae Acanthephyra brevicarinata 10A ,25 Acanthephyra brevicarinata 14A ,40 Acanthephyra brevicarinata 20A Acanthephyra brevicarinata 24A Hippolytidae Lebbeus scrippsi* 14B ,60 Nematocarcinidae Nematocarcinus cf. ensifer* 14A ,40 Nematocarcinus cf. ensifer* 14B ,60 Nematocarcinus cf. ensifer* Nematocarcinus cf. ensifer* 24A Pandalidae Heterocarpus affinis 10A ,25 Heterocarpus affinis 14A ,40 Heterocarpus affinis 20A Heterocarpus affinis Heterocarpus affinis 24A Crangonidae Paracrangon areolata* 14A ,40 Glyphocrangonidae Glyphocrangon spinulosa* 10A ,25 Glyphocrangon spinulosa* 24A Nephropidae Nephropsis occidentalis* 14B ,60 Ctenochelidae Callianopsis goniophthalma* 24A Axiidae Calocarides quinqueseriatus* 10A ,25 Polychelidae Stereomastis nana 14B ,60 Galatheidae Munidopsis depressa* Munidopsis depressa* 10A ,25 Munidopsis depressa* 14A ,40 Munidopsis depressa* 14B ,60 Munidopsis depressa* 24A Munidopsis diomedeae Munidopsis hystrix* 20A Atelecyclidae Trachycarcinus corallinus* 14B ,60 Oxygen content in the water column Analysis of the dissolved oxygen concentration measured close to bottom (Fig. 4) indicated critical hypoxic conditions at depths between 300 and 800 m. Values higher than 1.0 ml O 2 /l are found at ca m and there is a clear tendency for oxygen content to increase significantly in deeper water. Values obtained during the TALUD IV cruise in August 2000 are similar, although slightly higher, to those registered at a depth range of ca m during the TALUD III in August 1991 (Fig. 4). The vertical distribution of oxygen in the area (Fig. 5) indicates the presence

11 Continental slope decapod crustaceans southeastern Gulf of California 105 Fig. 4. Dissolved oxygen concentration measured near bottom during TALUD III and IV cruises. of three successive environments. The well-oxygenated epipelagic zone ranges from surface to about m, with oxygen concentration as high or higher than 2 ml/l. Deeper into the water column, a wide hypoxic to almost anoxic mesopelagic zone is found, extending roughly from m to m (or to the bottom in stations shallower than 800 m). The deep water benthic-demersal environment is almost anoxic in localities shallower than m but oxygen content is higher in deeper localities; oxygen reaches values of ml/l in the depth range of m. In deeper water, there is a strong recovery of the oxygen content, which progressively reaches values above 2.0 ml/l in depths greater than 2000 m (Fig. 4) Oxygen (ml/l) Oxygen (ml/l) Oxygen (ml/l) Oxygen (ml/l) Oxygen (ml/l) Station 9 Lat: Long: Water depth: 440 m 750 Station 10A Lat: Long: Water depth: 932 m 750 Station 14 Lat: Long: Water depth: 740 m 800 Station 1 Lat: Long: Water depth: Station 3 Lat: Long: Water depth: Oxygen (ml/l) Oxygen (ml/l) Oxygen (ml/l) Oxygen (ml/l) Oxygen (ml/l) Station 14A Lat: Long: Water depth: 1005 m 1000 Station 14B Lat: Long: Water depth: 1168 m 400 Station 15 Lat: Long: Water depth: 545 m 1200 Station 4 Lat: Long: Water depth: Station 5 Lat: Long: Water depth: Fig. 5. Vertical distribution of oxygen at selected stations; TALUD III (St. 9, 10A, 14, 14A, 14B and 15) and TALUD IV (St. 1, 3, 4 and 5) cruises.

12 106 Michel E. Hendrickx Occurrence of deep-water species A total of 31 species of decapod crustaceans living below 550 m was collected during both cruises (TALUD III, 15 species; TALUD IV, 26 species). Of these, 21 are typically benthic and eight are exclusively pelagic. Three species (Benthesicymus tanneri, Acanthephyra carinata and Nematocarcinus cf. ensiger) probably have a benthopelagic habitat as they have been collected with both benthic and pelagic gear; adults of these three species are heavy, and there might be a depth or habitat segregation among juveniles and adults. Six species of the deep water galatheid Munidopsis were collected. Considering the number of specimens collected, M. depressa appears as the dominant species (324 specimens at four stations) and no other species came near to this abundance. Four species were represented by 9-15 specimens during the entire 2000 survey (Benthesicymus tanneri, Nematocarcinius cf. ensifer, Heterocarpus affinis and Acantephyra brevicarinata) and the rest were even less abundant (Table 3 and text). The number of species at each station varied considerably. During TALUD III cruise, the highest number of species obtained at one single station was eight (station depth: m) and the lowest was one (Table 4). One station, at m, yielded only one species of isopod. No strictly pelagic species were recorded. As noted previously, the second cruise (TALUD IV) yielded a considerably higher number of species. The highest number of species was obtained at station 19 (15 benthic and one pelagic species), followed by station 26 (12 benthic and one pelagic species) (Table 3). Coincidentally, both samples were obtained in the m depth range and oxygen content was similar (0.73 and 0.76 ml 0 2 /l). The highest number of species during TALUD III cruise was obtained in similar conditions: at m, with oxygen content of 0.60 ml/l. Comparatively, the other stations feature a low species occurrence (Tables 3, 4). Oxygen content at bottom level does not seem to be a critical factor; indeed, the highest oxygen content during the TALUD IV cruise was measured at station 14 (2.44 ml O 2 /l) but only two benthic species were caught. The other two stations where oxygen content was above 1.0 ml/l are stations 13 (1.46 ml/l) and 35 (1.68 ml/l only two benthic species were collected) in both stations. Two stations had four species and both feature a low oxygen content (0.29 ml/l at station 25 and 0.61 ml/l at station 33). Results obtained during this survey allow us to determine the dissolved oxygen interval at which 21 species occur (Fig. 6), although for some species only one oxygen value is available. These intervals indicate that all these 21 species are occasionally found in hypoxic conditions, below 1.0 ml O 2 /l. Species occurrence with depth Combined depth occurrence of species for both cruises indicates that all species, except the Pagurid, were collected at least once within the depth range of m (Fig. 7). Only five species (A. brevicarinata, N. cf. ensifer, H. affinis, G. sicaria and M. diomedeae) range to deeper water. The widest bathymetric range corresponded to A. brevicarinata. Pasiphaea emarginata, together with P. magna, and these were recorded in the pelagic realm. Typically benthic species M. depressa, M. hystrix, G. spinulosa and H. affinis feature a relatively wide bathymetric distribution and were rather common in samples (see Tables 3, 4 and text); they dominate the m decapod crustacean community. Benthesicymus tanneri Acanthephyra Nematocarcinus cf. ensifer Lebbeus scrippsi Heterocarpus affinis Pandalus amplus Paracrangon areolata Sclerocrangon atrox Glyphocrangon sicaria Glyphocrangon spinulosa Nephropsis occidentalis Calocarides Stereomastis nana Stereomastis pacificus Munidopsis ciliata Munidopsis depressa Munidopsis diomedeae Munidopsis hystrix Munidopsis palmatus Munidopsis quadrata Trachycarcinus corallinus Fig. 6. Interval of epibenthic oxygen content corresponding to species collected during the TALUD III and IV cruises.

13 Continental slope decapod crustaceans southeastern Gulf of California 107 Benthesicymus tanneri Pasiphaea magna (P) Nematocarcinus cf. ensifer Heterocarpus affinis Paracrangon areolata Glyphocrangon spinulosa Calocarides quinqueseriatus Stereomastis pacificus Munidopsis depressa Munidopsis hystrix Munidopsis quadrata Trachycarcinus corallinus Fig. 7. Bathymetric range observed for species collected during the TALUD III and IV cruises. (P) probably pelagic species. DISCUSSION The total number of species collected during both surveys is 31. Of these, 15 were described by W. FAXON on the basis of material collected by the Albatross in The new results indicate a higher species occurrence in the m depth range, where hypoxic conditions still prevail, although measurements made near bottom level suggest a recovery in oxygen concentration at ca. 800 m. In the sampling area, oxygen content at bottom level does not seem to be a critical factor controlling species number, as expected. Fewer species were caught at stations with oxygen content in the range of ml/l than at stations with much lower oxygen content. It might be concluded that, although critically low oxygen content (i.e., < 0.5 ml/l) may represent an impediment for the establishment of a rich benthic fauna, a higher oxygen content does not necessarily favour the presence of a richer fauna. Other factors such as availability of food, nature of substrate or strong submarine currents could affect species occurrence. With epibenthic values close to 0.0 ml O 2 /l (see HENDRICKX, 1995b), the oxygen minimum zone that extends off the coast of the southeastern Gulf of California represented an insuperable barrier for outershelf species. Even species known to tolerate low oxygen content (e.g., Squilla biformis Bigelow, 1891, Solenocera mutator Burkenroad, 1938, Pleuroncodes planipes Stimpson, 1860) are not found in deeper water in the area, despite the fact that there are deep water records of these species in other areas (S. biformis, to 518 m; S. mutator, to m; P. planipes, to 366 m and exceptionally to 730 m) (HENDRICKX, 1995c, 1995d, 1995e). Not a single species belonging to the southeastern Gulf of California decapod crustaceans shelf community (107 species according to HENDRICKX, 1996a) was collected. The bathymetric fringe extending roughly from 1000 to 1380 m presents a particular interest for its species richness. Food supply and trophic relationships among these species and with large, highly mobile predators (e.g., fishes and squids) that were not sampled during this survey, probably due to the type of sampling gear that was used, are major issues to be addressed. Other major issues include the accessibility to species with fishing potential (e.g., Heterocarpus affinis, Pandalus ampla, Benthesicymus tanneri) and the evaluation of standing stock, for which larger and faster sampling gear will have to be used. ACKNOWLEDGEMENTS The author is grateful to Mercedes Cordero R. for editorial work and the bibliographic search for this manuscript. Scientists, students and crew members who took an active part during the TALUD III and IV cruises, in particular the technical staff (A. Toledano G., A. Nuñez P., A. Castro del Río, A. Galavíz S., and J. Salgado B.), are also thanked. I also thank G. Ramirez for processing the environmental data obtained during the TALUD IV cruise; the data obtained during the TALUD III cruise are courtesy of R. Thunell and his crew (University of South Carolina). TALUD IV was supported by CONACyT Project N. REFERENCES ALCOCK, A. W. (1901). A descriptive catalogue of the Indian deep-sea Crustacea Decapoda Macrura and Anomura, in the Indian Museum, being a revised account of the deep-sea species collected by the Royal Indian Marine Survey Ship Investigator. Calcutta: 1-286, pls ALLEN, J.A. & T.H. BUTLER. (1994). The Caridea (Decapoda) collected by the Mid-Pacific mountains expedition, Pac. Sci., 48(4):

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